The investigator's major research interest lies in studying the disposition of neurotransmitters at synapses and interactions with drugs that affect the brain. In the present grant we have devoted our major attention to histamine as a possible neurotransmitter in the brain. During the coming year we propose to continue this work. Since most of our efforts to date have been directed at an understanding of histamine in nerve terminals in the brain with no attention paid to the post- synaptic receptor, we hope to chemically study the histamine receptor. In these experiments we will make use of our techniques developed in the study of the opiate, glycine and acetylcholine receptors in the brain. These techniques involve use of ligands with high affinity for the receptor labeled radioactively with a high specific activity. An extensive series of examinations are performed to determine specificity of receptor binding.